Semiconductor devices and method of making the same

ABSTRACT

In one embodiment, the semiconductor devices relate to using one or more super junction trenches for termination.

BACKGROUND

This disclosure relates in general, to electronics, and moreparticularly though not exclusively, to semiconductors, structuresthereof, and methods of forming semiconductor devices.

Two major parameters which can be important to the high voltage powerswitch market are breakdown voltage (BV) and on-state resistance (RS).In typical systems a high breakdown voltage is desired. However, this isoften at the expense of high RS. A trade-off in performance whichaccompanies balancing a high breakdown voltage and a high RS is a majordesign challenge for manufacturers of high voltage power switchingdevices. An edge termination structure that surrounds a semiconductordevice aids in the reduction of electric fields at the edge of thesemiconductor device (edge electric fields). Some edge terminationstructures can include superjunctions separated by insulating pillars,which can be referred to as superjunction trenches. However, suchsuperjunction trenches typically prevent depletion from advancingfurther into the termination area.

Accordingly, it is desirable to have superjunction trenches that provideimproved charge depletion properties.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of present disclosure will become more fully understood fromthe detailed description and the accompanying drawings, which are notintended to limit the scope of the present disclosure.

FIG. 1A is a partial, cross-sectional view of one example of asemiconductor device in accordance with an embodiment of the presentdisclosure.

FIG. 1B is an enlarged plan view of the semiconductor device depicted inFIG. 1A.

FIG. 2 is a partial, cross-sectional view of one example of asemiconductor device in accordance with an embodiment of the presentdisclosure.

FIG. 3 is an enlarged plan view the semiconductor device depicted inFIG. 2.

FIG. 4 is an enlarged plan view of one example of a semiconductordevice.

FIG. 5A is a cross-sectional view of one example of region 480 ofsemiconductor device 400 as depicted in FIG. 4.

FIG. 5B is a cross-sectional view of one example of region 490 ofsemiconductor device 400 as depicted in FIG. 4.

FIG. 6 is an enlarged plan view of one example of a semiconductordevice.

FIGS. 7A-G[[J]] depict a non-limiting example of a process for making asuper-junction trench in accordance with an embodiment of the presentdisclosure.

For simplicity and clarity of the illustration, elements in the figuresare not necessarily to scale, are only schematic and are non-limiting,and the same reference numbers in different figures denote the sameelements, unless stated otherwise. Additionally, descriptions anddetails of well-known steps and elements are omitted for simplicity ofthe description. As used herein current carrying electrode means anelement of a device that carries current through the device such as asource or a drain of an MOS transistor or an emitter or a collector of abipolar transistor or a cathode or anode of a diode, and a controlelectrode means an element of the device that controls current flowthrough the device such as a gate of an MOS transistor or a base of abipolar transistor. Although the devices are explained herein as certainN-channel or P-Channel devices, or certain N-type or P-type dopedregions, a person of ordinary skill in the art will appreciate thatcomplementary devices are also possible. It will be appreciated by thoseskilled in the art that the words “during”, “while”, and “when” as usedherein relating to circuit operation are not exact terms that mean anaction takes place instantly upon an initiating action but that theremay be some small but reasonable delay, such as a propagation delay,between the reaction that is initiated by the initial action.Additionally, the term “while” means that a certain action occurs atleast within some portion of a duration of the initiating action. Theuse of the word “approximately” or “substantially” means that a value ofan element has a parameter that is expected to be close to a statedvalue or position. However, as is well known in the art there are alwaysminor variances that prevent the values or positions from being exactlyas stated. It is well established in the art that variances of up to atleast ten percent (10%) (and up to twenty percent (20%) forsemiconductor doping concentrations) are reasonable variances from theideal goal of exactly as described. When used in reference to a state ofa signal, the term “asserted” means an active state of the signal andinactive means an inactive state of the signal. The actual voltage valueor logic state (such as a “1” or a “0”) of the signal depends on whetherpositive or negative logic is used. Thus, “asserted” can be either ahigh voltage or a high logic or a low voltage or low logic depending onwhether positive or negative logic is used and negated may be either alow voltage or low state or a high voltage or high logic depending onwhether positive or negative logic is used. Herein, a positive logicconvention is used, but those skilled in the art understand that anegative logic convention could also be used. The terms “first”,“second”, “third” and the like in the Claims or/and in the DetailedDescription of the Drawings, are used for distinguishing between similarelements and not necessarily for describing a sequence, eithertemporally, spatially, in ranking or in any other manner. It is to beunderstood that the terms so used are interchangeable under appropriatecircumstances and that the embodiments described herein are capable ofoperation in other sequences than described or illustrated herein. Forclarity of the drawings, doped regions of device structures areillustrated as having generally straight line edges and precise angularcorners. However, those skilled in the art understand that due to thediffusion and activation of dopants the edges of doped regions generallymay not be straight lines and the corners may not be precise angles.

In addition, the description illustrates a cellular design (where thebody regions are a plurality of cellular regions) instead of a singlebody design (where the body region is comprised of a single regionformed in an elongated pattern, typically in a serpentine pattern).However, it is intended that the description is applicable to both acellular implementation and a single base implementation.

DETAILED DESCRIPTION

The present description includes, among other features, a semiconductordevice that has, among other features, a termination area having superjunction trenches with conductive regions that provide improved chargedepletion.

Processes, techniques, apparatuses, and materials as known by one ofordinary skill in the art may not be discussed in detail but areintended to be part of the enabling description where appropriate. Forexample specific methods of semiconductor formation may not be listedfor achieving each of the steps discussed; however one of ordinary skillwould be able, without undo experimentation, to establish the stepsusing the enabling disclosure herein. For example, semiconductorstructures can be formed by various processes including but not limitedto deposition processes, removal processes, patterning processes, andprocesses that modify the electrical properties. Non-limiting examplesof deposition processes include physical vapor deposition (PVD),chemical vapor deposition (CVD), electrochemical deposition (ECD),molecular beam epitaxy (MBE) and atomic layer deposition (ALD). Removalprocesses include any process that removes material either in bulk orselectively, some non-limiting example of which are etch processes,either wet etching or dry etching and chemical-mechanical planarization(CMP). Patterning includes processes that shape or alter the existingshape of the deposited materials for example lithography. Modificationof electrical properties includes doping. Non-limiting examples ofdoping processes can include rapid thermal annealing (RTA) andmodification of dielectric constants in low-k insulating materials viaexposure to ultraviolet light in UV processing (UVP).

Although the devices may be explained herein as certain conductivitytypes such as N-tpye or P-type, or described as certain N-channel orP-Channel devices, or certain N-type or P-type doped regions, a personof ordinary skill in the art will appreciate that complementary devicesare also possible. For example the regions can be of variousconductivity types, such as N-type or P-type, and various values ofresistivity or conductivity, such as N+, N−, P+, P−, N, and P, and canalso be formed by other than doping processes as known by one ofordinary skill.

Additionally somes embodiments of an edge termination structuredisclosed herein can be combined with any semiconductor device, forexample IGBTs, Junction-Schottky diodes, Silicon-on-Insulator (SOI)devices, and Thyristors.

FIG. 1 is a partial, cross-sectional view of one example of asemiconductor device in accordance with an embodiment of the presentdisclosure. FIG. 1 illustrates a semiconductor device 100, includingtermination area 102 and active region 104. Edge 106 of active region104 borders termination area 102. Active region 104 includes sourceelectrode 108 contacting source active cells and dielectric 110. In someembodiments, electrode 108 extends into termination area 102, but it maynot extend into termination area 102 in other embodiments. Electrode 108can be any conductive material, such as a metal. Super junction trench112 and super-junction trench 113 each include several pillars or layersformed vertically in the termination area (e.g., an epitaxy layer).Super-junction trench 112 and super-junction trench 113 can each havevarious combinations of conductivity types (e.g., N type, P type) forexample NP-buffer-PN or PN-buffer-NP In some embodiments, the buffer maybe a dielectric (e.g., a metal oxide), a void, or combinations thereof.The NP-buffer-PN or PN-buffer-NP pillar structures may facilitatedepletion. The depletion front from active region 104 passes throughepitaxial layer 114 and reaches the Pwell region 130 (e.g., a firstpwell region of the 1^(st) termination trench) at a given appliedvoltage (e.g., 100V), and consequently biasing and depleting the pwelland P-pillar on the both sides of the trench (pwell regions of 130 and132, and P-pillar regions of 118 and 124) through the conductive region134. This also helps to deplete the N-type pillar regions, and the N-epion both sides of the trench. As the voltage is further increased, thedepletion front extends out and subsequently biases and depletes thesimilar regions of the next trench, and follows on until the desiredbreakdown voltage is reached (e.g. 800V). When first region 116 isdepleting, second region 118 may also be depleting. In some embodiments,first region 116 and second region 118 have a different conductivitytype.

Buffer region or layer 122 (e.g., an insulator layer, an intrinsiclayer, an oxide layer, a gas region, a dielectric layer, a void, or acombination of layers and regions) can be positioned between secondregion 118 and third region 124 (e.g., a P-type pillar). During theprocess of depletion, the electro-static potential lines can extend intobuffer region 122.

Third region 124 is between buffer region 122 and fourth region 126(e.g., an N-type region). In some embodiments, third region 124 has adifferent conductivity type than fourth region 126. Fourth region 126 isadjacent to region 128 which may have a different conductivity type thanepitaxial layer 114, or have the same conductivity type as epitaxiallayer 114. In some embodiments, region 128 can be an extension ofepitaxial layer 114, and thus the same conductivity, in which superjunction trench 112 has been formed. Note in the non-limiting examplesdiscussed, the regions (e.g., first region 116, second region 118, thirdregion 124, and fourth region 126) can have various conductivity types(e.g., N-type and P-type) which can be acquired by methods known bythose of ordinary skill in the semiconductor fabrication, for example bydoping. Note that one region (e.g., first region 116) can also bedistinguished by another region (e.g., second region 118) by differentvalues of conductivity.

Second region 118 includes first p-well region 130 which is adjacent todielectric 110 and epitaxial layer 114. Meanwhile, third region 124includes second p-well region 132 which is adjacent to dielectric 110and region 128. Conductive region 134 extends between dielectric layer110 and dielectric region 140, and electrically couples first p-wellregion 130 and second p-well region 132. Conductive region 134 can be,for example, a metal or polysilicon. Thus, as shown, second region 118and third region 124 are shorted via first p-well region 130, secondp-well region 132, and conductive region 134. Thus, when second region118 is depleting, third region 124 may also be depleting, and therefore,depletion can occur on both sides of super junction trench 112. Thedepletion may further advance through region 128 and across superjunction trench 113. Accordingly, the super junction trenches areconfigured so that depletion can occur over two or more super-junctiontrenches. Also, without being bound to any particular theory, it isbelieved that p-well region 130 and p-well region 132 may screen highelectric fields formed near the top of first region 116 and fourthregion 126.

In some embodiments, electrode 108 and conductive region 134 may includethe same conductive material, such as a metal or polysilicon. Bothelectrode 108 and conductive region 134 may optionally be formed duringthe same process step, or at about the same time, when making thesemiconductor device. Dielectric region 140 may also be the same ordifferent material than dielectric layer 110. For example, dielectricregion 140 and dielectric layer 110 may both be silica.

In some embodiments, the super junction trenches can include n-wellregions electrically coupled to the second region and the third region.For example, the super junction trench may have a PN-buffer-NPconfiguration, where the second region and the third region both haveN-type conductivity and each include n-well regions that areelectrically coupled by a conductivity region.

Super junction trench 113 also includes second region 118 and thirdregion 124 which are shorted so that depletion may also advance toregion 136. Region 136 may have the same or different conductivity typeas epitaxial layer 114. In some embodiments, region 136 and region 128can both be an extension of epitaxial layer 114, and thus the sameconductivity, in which super junction trench 112 and super junctiontrench 113 have been formed.

The super junction trenches may, in some embodiments, include aconductive region that extends through the buffer region rather than thedielectric layer. As an example, conductive region 134 may extendthrough buffer region 122 to electrically couple second region 118 andthird region 124. The conductive region may be formed, for example, byfilling the top of a trench containing the buffer region with aconductive material, such as a metal, polysilicon or silicon epi plug.Furthermore, the p-well regions in the super junction trenches (e.g.,p-well region 130 and p-well region 132 in super-junction trench 112)are optional, and therefore, in some embodiments, the super-junctiontrenches do not include p-well regions.

In some embodiments, the first semiconducting region and the fourthsemiconducting region are formed from a common layer (e.g., first dopedlayer 745 forms the first semiconducting region and the secondsemiconducting region as depicted in FIG. 7G). In some embodiments, thesecond semiconducting region and the third semiconducting region areformed from a common layer (e.g., second doped layer 750 forms the firstregion and the second region as depicted in FIG. 7G).

FIG. 1B is an enlarged plan view of the semiconductor device depicted inFIG. 1A. Semiconductor device 100 includes semiconductor die 160 havingactive region 104 formed thereon. Super junction trench 113 and superjunction trench 112 each form closed ring structures that surroundactive region 104.

The semiconductor devices may, in some embodiments, include two or moresuper-junction trenches (e.g., two, three, four, five, six, or moresuper-junction trenches) having a second region and a third region thatare shorted (e.g., second region 118 and third region 124 insuper-junction trench 112 as depicted in FIG. 1A). Thus, thesemiconductor devices can have a depletion region that extends overmultiple super-junction trenches. In some embodiments, an epitaxiallayer is disposed between each pair of the super junction trenches. Theskilled artisan, guided by the teachings of the present disclosure, willappreciate that the number and spacing between the super junctiontrenches can be modified to adjust the depletion characteristics of thetermination area. For example, the spacing between super junction trench112 and super junction trench 113 may be modified to adjust depletioncharacteristics. In some embodiments, the distance between adjacenttrenches can be about 5 to 20 microns. The distance between adjacenttrenches may vary. For example, the distance between adjacent trenchesmay increase as the approach the edge of the die. In some embodiments,the super junction trenches comprise pillars (e.g., first semiconductingregion 116, second semiconducting region 118, buffer region 122, thirdsemiconducting region 124, and fourth semiconducting region 126 in superjunction trench 112) that each have a width of about 0.1 μm to about 10μm, or about 0.2 μm to about 2 μm.—Note that buffer regions can includeseveral types of layers of dielectrics and insulators. For example,buffer region 122 can include an oxide layer and a gas region. Thepillars or buffer regions in each super junction trench may be in thesame or different relative to other super-junction trenches in thetermination area.

Note that discussions herein may refer to a layer or a region where alayer is a specific type of region, generally formed parallel to asurface. A region can be of any shape of formation. Thus, although somenon-limiting examples discuss layers, the scope of such embodimentsshould be interpreted to extend to also include regions. Note that thesuper-junction trench (e.g., super junction trench 112) can beoperatively attached to the epitaxial layer (e.g., epitaxial layer 114),where operatively attached includes formed in and/or adjacent to theepitaxial layer.

FIG. 2 is a partial, cross-sectional view of one example of asemiconductor device in accordance with an embodiment of the presentdisclosure. Semiconductor device 200 includes generally the samestructures as semiconductor device 100 depicted in FIG. 1. Consequently,features 202-240 depicted in FIG. 2 correspond to features 102-140depicted in FIG. 1. For example, super-junction trench 212 andsuper-junction trench 213 have the same characteristics assuper-junction trench 112 and super junction trench 113, respectively.

Semiconductor device 200 also includes super junction trench 238 havingfirst semiconducting region 241, second semiconducting region 242,buffer region 244, third semiconducting region 246, and fourthsemiconducting region 248. Super junction trench 238 can have variouscombinations of conductivity types (e.g., N type, P type) for exampleNP-buffer-PN or PN-buffer-NP. In some embodiments, the buffer may be adielectric (e.g., a metal oxide), a void, or combinations thereof. TheNP-buffer-PN or PN-buffer-NP pillar structures may facilitate depletion.Super junction trench 238 does not include a conductive region thatelectrically couples second region 242 and third region 246 (e.g., doesnot include conductive region 234 in super junction trench 213). Thus,in some embodiments, second region 242 is insulated from third region246. Semiconductor device 200 may therefore be configured so thatdepletion may advance across super-junction trench 212 and superjunction trench 213 via conductive region 234, but depletion acrosssuper junction trench 238 may be diminished (or preventing the fieldfrom spreading beyond the buffer region) because second region 242 isinsulated from third region 246. Semiconductor device 200 may therefore,in some embodiments, advantageously prevent or reduce an electric fieldnear an edge of semiconductor device 200.

Region 250 in semiconductor device 200 can have the same or differentconductivity type a region 236, region 228, and epitaxial layer 214. Insome embodiments, region 250, region 236, and region 228 can each be anextension of epitaxial layer 214, and thus the same conductivity, inwhich super-junction trench 212, super junction trench 213, andsuper-junction trench 238 have been formed.

The semiconductor devices may, in some embodiments, include one or more(e.g., one, two, three, four, five, six, or more) super junctiontrenches having a second semiconducting region that is shorted to athird semiconducting region (e.g., super junction trench 212 andsuper-junction trench 213 as depicted in FIG. 2) and one or more (e.g.,one, two, three, four, five, six, or more) super junction trencheshaving a second semiconducting region that is insulated from a thirdsemiconducting region (e.g., super junction trench 238 as depicted inFIG. 2). The super-junction trenches having a second semiconductingregion that is shorted to a third semiconducting region can be betweenthe active region and the super junction trenches having a secondsemiconducting region that is insulated from a third semiconductingregion. For example, super-junction trench 212 and super-junction trench213 are both between active region 204 and super-junction trench 238 asdepicted in FIG. 2.

Note that doping levels in some embodiments can vary. As a non-limitingexample, N doped and P doped regions can have concentrations on theorder of about 1×10¹³ to about 1×10¹⁸ atoms/cm³, and more particularlyconcentrations on the order of 1×10¹⁵ to about 1×10¹⁷ atoms/cm³.Intrinsic layers are undoped or lightly doped regions with a dopantconcentration less than about 2×10¹⁴ atoms/cm³. Additionally theintrinsic layer thickness can vary, for example between about fifty (50)nanometers and about two (2) microns. Additionally although the first,second, and third conductivity types (N-type and P-type) can be obtainedvia doping, other methods as known by one of ordinary skill in the artof semiconductor fabrication can be used to obtain regions of various Nand P conductivity types by other methods.

FIG. 3 is an enlarged plan view of semiconductor device 200 depicted inFIG. 2. Semiconductor device 200 includes semiconductor die 260 havingactive region 204 formed on semiconductor die 260. Super-junction trench238, super junction trench 212, and super-junction trench 213 each formclosed ring structures that surround active region 104.

FIG. 4 is an enlarged plan view of one example of a semiconductordevice. Semiconductor device 400 includes semiconductor die 410 havingtermination area 420 and active region 430. Termination area 420includes ring structure 440 and ring structure 450, which both surroundactive region 430. Ring structure 440 includes first segment 460 andsecond segment 465, which are alternatively arranged to form ringstructure 440 which surrounds ring structure 450 and active region 430.Ring structure 450 includes first segment 470 and second segment 475,which are alternatively arranged to form ring structure 450 whichsurrounds active region 430.

FIG. 5A is a cross-sectional view of one example of region 480 ofsemiconductor device 400 as depicted in FIG. 4. Semiconductor device 400includes structures 502-510, which can be the same as structures 102-110in FIG. 1, respectively. Region 512 includes p-well region 514 and isbetween epitaxial layer 516 and region 518. As will be discussed furtherbelow, region 512 is a cross-section of second segment 475 of ringstructure 450. Meanwhile, region 518 can have the same or differentconductivity type as epitaxial layer 516. In some embodiments, region518 can be an extension of epitaxial layer 514, and thus the sameconductivity. Similarly, region 512 may be an extension of epitaxiallayer 514, and thus the same conductivity, in which p-well region 514has been formed.

Super junction trench 520 is between region 518 and region 521.Super-junction trench 520 can have generally the same characteristics assuper junction trench 238 as depicted in FIG. 2. Accordingly, firstsemiconducting region 522, second semiconducting region 524, bufferregion or layer 528, third semiconducting region 530, and fourthsemiconducting region 532 may have the same characteristics as firstsemiconducting region 240, second semiconducting region 242, bufferregion or layer 244, third semiconducting region 246, and fourthsemiconducting region 248, respectively. As an example, super junctiontrench 520 can have various combinations of conductivity types (e.g., Ntype, P type) for example NP-buffer-PN or PN-buffer-NP. Super junctiontrench 520 has second region 524 insulated from third region 530 anddoes not include a conductive region that electrically couples secondregion 524 and third region 530. As will be discussed further below,super-junction trench 520 is a cross-section of first segment 460 ofring structure 440. Region 521 in semiconductor device 400 can have thesame or different conductivity type as region 518, and epitaxial layer516. In some embodiments, region 518 and region 521 can each be anextension of epitaxial layer 516, and thus the same conductivity, inwhich super-junction trench 520 and p-well region 514 are formed.

FIG. 5B is a cross-sectional view of one example of region 490 ofsemiconductor device 400 as depicted in FIG. 4. Super junction trench534 is between epitaxial layer 516 and region 518. Super-junction trench534 can have generally the same characteristics as super-junction trench238 as depicted in FIG. 2. Accordingly, first semiconducting region 536,second semiconducting region 538, buffer region or layer 540, thirdsemiconducting region 542, and fourth semiconducting region 544 may havethe same characteristics as first semiconducting region 240, secondsemiconducting region 242, buffer region or layer 244, thirdsemiconducting region 246, and fourth semiconducting region 248,respectively. Super junction trench 534 may have the same or differentconfiguration as super junction trench 520. As an example,super-junction trench 534 may have a NP-buffer-PN configuration, whilesuper junction trench 520 may have a PN-buffer-NP configuration. Asanother example, super junction trench 534 and super-junction trench 520may both have NP-buffer-PN configuration.

Super junction trench 534 corresponds to first segment 470 in ringstructure 450 of semiconductor device 400. Thus, super junction trench534 as depicted in FIG. 5B and region 512 as depicted in FIG. 5A arealternatively arranged to form ring structure 450. P-well region 514 canbe adjacent to second region 538 and third region 542 of super junctiontrench 534 at each interface between first segment 470 and secondsegment 475 in ring structure 450. P-well region 514 may thereforeelectrically couple second region 538 and third region 542 ofsuper-junction trench 534 at each interface between first segment 470and second segment 475 in ring structure 450. Accordingly, chargedepletion can advance from active region 430 to second region 538 insuper junction trench 534 and then along ring structure 450 (e.g.,perpendicular to the cross-sectional view in FIG. 5B) to p-well region514 so that depletion may advance passed buffer region 540. Meanwhile,charge depletion may also directly advance from active region 430through region 512 without advancing through second region 538.

Region 546 includes p-well region 548 and is between region 518 andregion 521. Region 546 can, in some embodiments, be an extension ofepitaxial layer 516 in which p-well region 548 is formed. Region 546corresponds to second segment 465 in ring structure 440 of semiconductordevice 400. Thus, region 546 as depicted in FIG. 5B and super-junctiontrench 520 as depicted in FIG. 5A are alternatively arranged to formring structure 440. P-well region 548 can be adjacent to secondsemiconducting region 524 and third semiconducting region 530 of superjunction trench 520 at each interface between first segment 460 andsecond segment 455 in ring structure 440. P-well region 548 maytherefore electrically couple second semiconducting region 524 and thirdsemiconducting region 530 of super junction trench 520 at each interfacebetween first segment 460 and second segment 465 in ring structure 440.Accordingly, charge depletion can advance from ring structure 450 tosecond region 524 in super junction trench 520 and then along ringstructure 440 (e.g., perpendicular to the cross-sectional view in FIG.5A) to p-well region 548 so that depletion may advance passed bufferregion 528. Meanwhile, another portion of the charge depletion maydirectly advance from ring structure 450 through region 546.

In some embodiments, the semiconductor device may not include p-wellregions in the second segments of the ring structures. For example,referring to FIGS. 4 and 5A, region 546 in second segment 465 of ringstructure 440 may not include p-well region 548, but rather region 518,region 546, and region 522 may form a continuous portion of theepitaxial layer in which super-junction trench 534 is formed. In thiscase, second segment 546 is a “gap” in super-junction trench 520depicted in FIG. 5A which permits charge depletion to advance passedsuper-junction trench 520.

Referring again to FIG. 4, first segment 460 and first segment 470 areoffset relative to each other. This may prevent a straight path forcharge depletion from active region 430 to the edge of termination area420. Rather, this configuration requires a path that includes advancingparallel to first segment 460 and/or first segment 470 which bothinclude super-junction trenches.

FIG. 6 is an enlarged plan view of one example of a semiconductordevice. Semiconductor device 600 includes semiconductor die 610 havingtermination area 620 and active region 630. Termination area 620includes ring structure 640, ring structure 650, and ring structure 660,which each surround active region 630. Ring structure 640 can have thesame characteristics as ring structure 450 depicted in FIG. 4. Ringstructure 650 can have the same characteristics as ring structure 440depicted in FIG. 4. Ring structure 660 can be a continuous ring (e.g.,does not contain different segments) formed by a super junction trench.In some embodiments, the super junction trench has the samecharacteristics as super junction trench 238 depicted in FIG. 2. Thatis, the super junction trench includes a second semiconducting regionthat is insulated from a third semiconducting region. Ring structure 660may therefore prevent or greatly diminish charge depletion advancing tothe edge of termination area 620. Alternatively, in some embodiments,the super junction trench in ring structure 660 has the samecharacteristics as super-junction trench 113 depicted in FIG. 1.

The skilled artisan, guided by the teachings of the present disclosure,will appreciate that various combinations and types of continuous ringstructures (e.g., ring structure 660 as depicted in FIG. 6) andsegmented ring structures (e.g., ring structure 440 as depicted in FIG.4) can be selected to modulate the depletion properties of thetermination area. For example, the continuous ring structures can eachindependently have (i) a super junction trench having the second regioninsulated from the third region (e.g., super junction trench 238 asdepicted in FIG. 2) or (ii) a super junction trench having the secondregion electrically coupled to the third region (e.g., super junctiontrench 112 depicted in FIG. 1). The termination area may include one,two, three, or more continuous ring structures that may be the same ordifferent. Similarly, the segmented ring structures can eachindependently include two or more (e.g., two, three, four, or more)segments types that include at least two of: (i) a super junction trenchhaving the second semiconducting region insulated from the thirdsemiconducting region (e.g., super-junction trench 238 as depicted inFIG. 2); (ii) a super-junction trench where the second semiconductingregion is electrically coupled to the third semiconducting region (e.g.,super-junction trench 112 depicted in FIG. 1); (iii) a region having ap-well region (e.g., region 512 as depicted in FIG. 5A); and (iv) a“gap” in the ring structure (e.g., region 512 as depicted in FIG. 5A butwithout p-well region 514). The termination area may include one, two,three, four, five, six, or more segmented ring structures that may bethe same or different. Furthermore, the relative length and number ofthe segments may also be adjusted to modulate the depletion propertiesof the termination area.

Some embodiments disclosed herein include a method for making asemiconductor edge termination structure. The method may be used, forexample, to form the super-junction trenches disclosed in the presentdisclosure (e.g., super-junction trench 112 depicted in FIG. 1).

FIGS. 7A-J depict a non-limiting example of a process for making asuper-junction trench in accordance with an embodiment of the presentdisclosure. Those skilled in the art will appreciate that the methodsteps disclosed herein are one example of a method and that variationsof the method may be used. FIG. 7A shows doped semiconductor layer 705(e.g. N-doped epitaxy layer) formed on doped (e.g., N+ doped)semiconductor substrate 710. Dielectric layer 715 can be formed on dopedsemiconductor layer. First doped region 720 having a first conductivitycan be selectively formed as shown in FIG. 7B. First doped region 720may, for example, have a p-type conductivity and be formed by ionimplantation.

Referring to FIG. 7C, first recess 730 (e.g., a first trench) can beetched into semiconductor layer 705 using known semiconductor etchingtechniques. The vertical extent of the trench can reach semiconductorsubstrate 710, the semiconductor layer 705, or into a buffer region (notshown). First doped layer 745 having a second conductivity can be formedon, over, or adjoining the surface of recess 730 as shown in FIG. 7D. Insome embodiments, the conductivity of first doped layer 745 is differentthan the conductivity of first doped region 720. As an example, firstdoped region 720 can have a p-type conductivity, while first doped layer745 can have an n-type conductivity. First doped layer 745 can beformed, for example, using conventional selective epitaxial growthtechniques. In some embodiments, a selective etching process, such asdry etching, may be used to divide first doped layer 745 into separatepillars on each side of recess 730 (not shown).

Second doped layer 750 having a third conductivity can be formed on,over, or adjoining the surface of first doped layer 745. In someembodiments, the conductivity of second doped layer 750 can be the sameas the conductivity of first doped region 720. For example, first dopedregion 720 and second doped layer 750 can both have a p-typeconductivity. Second region 750 can be formed, for example, usingconventional selective epitaxial growth techniques. In some embodiments,a selective etching process may be used to divide second doped layer 750into separate pillars on each side of recess 730 (not shown).

Dielectric layer 755 can be formed on, over, or adjoining the surface ofsecond doped layer 750. In some embodiments, dielectric layer 755 maysubstantially fill the region between second doped layer 750 and recess730 (not shown).

As shown in FIG. 7E, second doped layer 750 can be electricallyconnected to first doped region 720 on both sides of recess 730. Forexample, first doped region 720 and second doped layer 750 may both havethe same conductivity type (e.g., p-type). Regions between first dopedregion 720 and second doped layer 750 can be passivated and doped using,for example, wet oxidation and ion implantation. A dielectric cap may beformed over recess 730 and the surface of the dielectric cap anddielectric layer 715 planarized.

In some embodiments, a conductive cap or region having, for example, ametal or polysilicon, can be used to cap recess 730 (not shown). Theconductive cap may electrically couple first doped region 720 on bothsides of first doped layer 745.

Conductive region 760 may be formed on dielectric layer 715 andconfigured to electrically couple first doped region 720 on both sidesof recess 730 as shown in FIG. 7F. For example, dielectric layer 715 canbe etched to expose first doped region 720 on both sides of first dopedlayer 745. Conductive layer 760 can then be formed using, for example,chemical vapor deposition. Additional dielectric material can be appliedon conductive layer 760 and the surface planarized as shown in FIG. 7G.In some embodiments, the method does not include forming conductiveregion 760 (e.g., in some embodiments including a conductive cap).

The skilled artisan, guided by the teachings of the present disclosure,will appreciate that the various operations disclosed for the method offorming the termination structure may be performed in a different orderand some operations may be performed at about the same time.

From all the foregoing one skilled in the art can determine thataccording to one embodiment, a semiconductor device comprises asemiconducting device. The semiconducting device may, in someembodiments, include a semiconductor substrate of a first conductivitytype and a first semiconducting layer of the first conductivity typeoverlying the semiconductor substrate.

In some embodiments, the semiconducting device includes an edgetermination structure having one or more first super junction trenches.In some embodiments, the first super-junction trenches each include: afirst semiconducting region; a second semiconducting region adjacent tothe first semiconducting region; a first buffer region adjacent to thesecond semiconducting region; a third semiconducting region adjacent tothe first buffer region; a fourth semiconducting region adjacent to thethird region; and a first conducting region electrically coupling thesecond region to the third region.

In some embodiments, the first semiconducting region has a secondconductivity type. In some embodiments, the second semiconducting regionhas a third conductivity type that is different than the secondconductivity type. In some embodiments, the third semiconducting regionhas the third conductivity type. In some embodiments, the fourthsemiconducting region has the second conductivity type.

Those skilled in the art will also appreciate that according to anotherembodiment of a semiconducting device having a semiconductor substrateof a first conductivity type, a first layer of the first conductivitytype overlying the semiconductor substrate, an active region; and one ormore ring structures surrounding the active region.

In some embodiments, the ring structures each include two or more firstsegments and two or more second segments. In some embodiments, each ofthe first segments includes a first super junction trench. In someembodiments, the first super junction trench includes: a firstsemiconducting region; a second semiconducting region adjacent to thefirst semiconducting region; a first buffer region adjacent to thesecond semiconducting region; a third semiconducting region adjacent tothe first buffer region; and a fourth semiconducting region adjacent tothe third region; and a first conducting region electrically couplingthe second region to the third region.

In some embodiments, the first semiconducting region has a secondconductivity type. In some embodiments, the second semiconducting regionhas a third conductivity type that is different than the secondconductivity type. In some embodiments, the third semiconducting regionhas the third conductivity type. In some embodiments, the fourthsemiconducting region has the second conductivity type.

In some embodiments, the second segments each include a fifthsemiconducting region having the first conductivity type. In someembodiments, the first segments and the second segments arealternatively arranged to form the ring structure.

Those skilled in the art will also appreciate that according to anotherembodiment of a method of forming a semiconductor edge terminationstructure. The method may, in some embodiments, include: forming atrench in an epitaxial layer; forming a first semiconducting layeroverlying a first sidewall of the trench; forming a secondsemiconducting layer overlying a second sidewall of the trench; forminga third semiconducting layer overlying the first semiconducting layer;forming a fourth semiconducting layer overlying the secondsemiconducting layer; forming a buffer layer between the thirdsemiconducting layer and the fourth semiconducting layer; and forming afirst conducting layer.

In some embodiments, the trench extends to a semiconductor substrate,and the semiconductor substrate and the epitaxial layer both have afirst conductivity type. In some embodiments, a conductivity type of thefirst semiconducting layer is the same as a conductivity type of thesecond semiconducting layer. In some embodiments, a conductivity type ofthe third layer is different than a conductivity type of the firstlayer. In some embodiments, a conductivity type of the fourthsemiconducting layer is different than a conductivity type of the secondsemiconducting layer. In some embodiments, the conductive regionelectrically couples the second semiconducting layer and the thirdsemiconducting layer.

As the claims hereinafter reflect, inventive aspects may lie in lessthan all features of a single foregoing disclosed embodiment. Thus, thehereinafter expressed claims are hereby expressly incorporated into thisDetailed Description of a non-limiting sample of embodiments, with eachclaim standing on its own as a separate embodiment of an invention.Furthermore, while some embodiments described herein include some butnot other features included in other embodiments, combinations offeatures of different embodiments are meant to be within the scope ofthe disclosure, and form different embodiments, as would be understoodby those skilled in the art. Such variations are not to be regarded as adeparture from the spirit and scope of the present disclosure.

In view of the above, it is evident that a novel device and method isdisclosed that can, in at least one embodiment, having a terminationarea with one or more super-junction trenches that provide improvedcharge depletion.

While the subject matter of the invention is described with specificpreferred embodiments and example embodiments, the foregoing drawingsand descriptions thereof depict only typical embodiments of the subjectmatter and are not therefore to be considered to be limiting of itsscope, it is evident that many alternatives and variations will beapparent to those skilled in the art.

As the claims hereinafter reflect, inventive aspects may lie in lessthan all features of a single foregoing disclosed embodiment. Thus, thehereinafter expressed claims are hereby expressly incorporated into thisDetailed Description of the Drawings, with each claim standing on itsown as a separate embodiment of an invention. Furthermore, while someembodiments described herein include some but not other featuresincluded in other embodiments, combinations of features of differentembodiments are meant to be within the scope of the invention, and formdifferent embodiments, as would be understood by those skilled in theart.

1. A semiconductor device comprising: a semiconductor substrate of afirst conductivity type; a first semiconducting layer of the firstconductivity type overlying the semiconductor substrate; and an edgetermination structure comprising one or more first super-junctiontrenches, wherein the first super-junction trenches each comprise: afirst semiconducting region having a second conductivity type; a secondsemiconducting region adjacent to the first semiconducting region,wherein the second semiconducting region has a third conductivity typethat is different than the second conductivity type; a first bufferregion adjacent to the second region; a third semiconducting regionadjacent to the first buffer region, wherein the third semiconductingregion has the third conductivity type; a fourth semiconducting regionadjacent to the third region, wherein the fourth region has the secondconductivity type; and a first conducting region electrically couplingthe second region to the third region.
 2. The semiconductor device ofclaim 1, wherein the first conductivity type is a n-type conductivityand the second conductivity type is a n-type conductivity.
 3. Thesemiconductor device of claim 1, wherein the third conductivity type isa p-type conductivity.
 4. The semiconductor device of claim 1, whereinthe first buffer region comprises a dielectric material and at least onevoid.
 5. The semiconductor device of claim 1, wherein the conductingregion is adjacent to the first buffer region.
 6. The semiconductordevice of claim 1, wherein: the second semiconducting region comprises afirst p-well region, wherein the first semiconducting region is at leastpartially disposed between the first p-well region and the first bufferregion; and the third semiconducting region comprises a second p-wellregion, wherein the fourth semiconducting region is at least partiallydisposed between the second p-well region and the first buffer region.7. The semiconductor device of claim 6, wherein the first conductiveregion electrically couples the first p-well region and the secondp-well region.
 8. The semiconductor device of claim 1, furthercomprising a dielectric layer formed on at least a portion of the firstsemiconducting region.
 9. The semiconductor device of claim 8, whereinthe first conductivity region extends through the dielectric layer. 10.The semiconductor device of claim 1, wherein the edge terminationstructure further comprises one or more second super-junction trenches,wherein the second super-junction trenches each comprise: a fifthsemiconducting region having a fourth conductivity type; a sixthsemiconducting region adjacent to the fifth semiconducting region,wherein the sixth semiconducting region has a fifth conductivity typethat is different than the fourth conductivity type; a second bufferregion adjacent to the sixth region; a seventh semiconducting regionadjacent to the first buffer region, wherein the seventh semiconductingregion has the fifth conductivity type; and an eighth semiconductingregion adjacent to the seventh region, wherein the eighth region has thefourth conductivity type, wherein the sixth region is electricallyinsulated from the seventh region.
 11. The semiconductor device of claim10, wherein the first super-junction trenches are disposed between thesecond super-junction trenches and an active region of the semiconductordevice.
 12. The semiconductor device of claim 10, wherein the fourthconductivity type is a n-type conductivity.
 13. The semiconductor deviceof claim 10, wherein the fifth conductivity type is a p-typeconductivity.
 14. The semiconductor device of claim 10, wherein thesecond buffer region comprises a dielectric material and at least onevoid.
 15. A semiconducting device comprising: a semiconductor substrateof a first conductivity type; a first layer of the first conductivitytype overlying the semiconductor substrate; an active region; and one ormore ring structures surrounding the active region, the ring structureseach comprising: two or more first segments each comprising a firstsuper-junction trench, wherein the first super-junction trenchcomprises: a first semiconducting region having a second conductivitytype; a second semiconducting region adjacent to the firstsemiconducting region, wherein the second semiconducting region has athird conductivity type that is different than the second conductivitytype; a first buffer region adjacent to the second region; a thirdsemiconducting region adjacent to the first buffer region, wherein thethird semiconducting region has the third conductivity type; and afourth semiconducting region adjacent to the third region, wherein thefourth region has the second conductivity type; two or more secondsegments each comprising a fifth semiconducting region having the firstconductivity type, wherein the first segments and the second segmentsare alternatively arranged to form the ring structure.
 16. Thesemiconducting device of claim 15, wherein the second segments eachfurther comprise a sixth region having the third conductivity type,wherein the sixth region is electrically connected to the secondsemiconducting region and the third semiconducting region of one or moreof the super-junction trenches.
 17. The semiconducting device of claim15, further comprising one or more continuous ring structures eachcomprising a second super-junction trench, where the secondsuper-junction trench comprises: a sixth semiconducting region having afourth conductivity type; a seventh semiconducting region adjacent tothe sixth semiconducting region, wherein the seventh semiconductingregion has a fifth conductivity type that is different than the fourthconductivity type; a second buffer region adjacent to the seventhregion; an eighth semiconducting region adjacent to the second bufferregion, wherein the eighth semiconducting region has the fifthconductivity type; and a ninth semiconducting region adjacent to theeighth region, wherein the ninth region has the fourth conductivitytype, wherein the seventh region is electrically insulated from theeighth region.
 18. The semiconductor of claim 17, wherein the ringstructures are enclosed within the continuous ring structures.
 19. Amethod of forming a semiconductor edge termination structure comprising:forming a trench in an epitaxial layer, wherein the trench extends to asemiconductor substrate, and the semiconductor substrate and theepitaxial layer both have a first conductivity type; forming a firstsemiconducting layer overlying a first sidewall of the trench; forming asecond semiconducting layer overlying a second sidewall of the trench,wherein a conductivity type of the first semiconducting layer is thesame as a conductivity type of the second semiconducting layer; forminga third semiconducting layer overlying the first semiconducting layer,wherein a conductivity type of the third layer is different than aconductivity type of the first layer; forming a fourth semiconductinglayer overlying the second semiconducting layer, wherein a conductivitytype of the fourth semiconducting layer is different than a conductivitytype of the second semiconducting layer; forming a buffer layer betweenthe third semiconducting layer and the fourth semiconducting layer; andforming a first conducting layer that electrically couples the secondsemiconducting layer and the third semiconducting layer.
 20. The methodof claim 19, wherein the first semiconducting layer and the fourthsemiconducting layer both have an n-type conductivity.